The present invention relates to a method and an apparatus for cutting a braided sheath away from the terminal of a shielding wire by a prescribed length.
A shielding wire is constructed in such a manner that a conductor S1 is covered by an internal insulating material S2, and then covered by a braided sheath S3 having conductivity thereon, and then by an outer insulating jacket S4 in succession, as shown in FIG. 14.
In order to connect a terminal or the like to the terminal of the shielding wire A, the outer jacket S4 is stripped away from the terminal thereof by a prescribed length, and then the braided sheath S3 is reversed and folded back onto the outer jacket S4 or cut off by an appropriate length, and thereafter the exposed internal insulating material S2 is stripped off by a prescribed length to expose the conductor S1.
As one of methods for cutting a braided sheath away in such terminal processing, the braided sheath may be incised from the periphery thereof by means of a cutting tool and removed, concurrently with strip-off operation of the outer jacket.
There is another method for cutting a braided sheath away which comprises the steps of: holding the portion in the vicinity of the tip of the exposed braised sheath by means of internal blades of the two-piece cutting tool after the outer jacket is stripped off; moving the internal blades toward the other end of the wire to loosen and dilate the portion of braided sheath corresponding to the section between the cut end of the outer jacket and the internal blades radially; and cutting the dilated portion of the braided sheath created in front of the internal blades by intersecting the external blade therewith.
However, the former of the above-described methods has a disadvantage in that when cutting the braided sheath, the blade may damage the internal insulating material in case where the blade reaches the internal insulating material.
While the latter of the above-described methods has no possibility to damage the internal insulating material because the braided sheath is cut after it is isolated from the internal insulating material. However, this method is operable only when the length to be stripped off is longer than the length to be held by the internal blades, which gives limitations to the conditions of processing (the length to be stripped off).
In order to avoid the disadvantages hitherto described, the present invention proposes a method and an apparatus for cutting a braided sheath, which does not damage the internal insulating material and gives fewer limitations to the processing conditions.
As a measure to solve the problems described so far, the present invention provides a method for cutting a braided sheath of a shielding wire comprising the steps of: widening a tip of the braided sheath exposed at a terminal portion of the shielding wire by stripping an outer jacket into a shape of a funnel; holding a periphery of a portion of the braided sheath not to be removed with internal blades in a shape of a two-piece cylinder; moving the shielding wire including the internal blades relative to a cylindrical external blade opposed to the internal blades along a longitudinal direction of the wire with respect to each other; inserting the external blade from the terminal side of the wire between the braided sheath and the internal insulating material; and cutting the portion of the braided sheath isolated from the internal insulating material by means of the external blade and the internal blades.
As an apparatus to perform this method, there is provided an apparatus comprising; a clamp mechanism for registering and holding the shielding wire at the center of the position where a processing is carried out; a widening mechanism for widening the tip of the braided sheath which is exposed at the terminal of the wire by stripping the outer jacket off; and a cutting mechanism including the internal blades disposed in the shape of a two-piece cylinder and a cylindrical external blade supported by a slider and opposed to the internal blades.
Preferably, the cutting apparatus of the present invention further comprises a sliding mechanism for moving the internal blades along a longitudinal direction of the wire; and a suction unit for collecting chips of the braided sheaths, wherein, upon completion of cutting operation, the external blade is retracted, the internal blades moves toward the external blade to remove the chip of the braided sheath, and the chips is sucked and collected by means of the suction unit waiting thereunder.
Preferably, the widening mechanism to be used in this apparatus warps the tip of the braided sheath by pressing the portion in the vicinity of the tip thereof from the outside, then grasps the portion of the braided sheath not to be removed with a clamp having grooves of a semi-circular cross section, and inserts a cylindrical body between the braided sheath with the tip widened outwardly and the internal insulating material to further widen the area of the braided sheath to be removed with the cylindrical body.
In the method and apparatus according to the present invention, the braided sheath is cut off by the steps of inserting the cylindrical external blade into the interior of the braided sheath widened in the shape of a funnel to isolate the cutting point of the braided sheath from the internal insulating material of the wire, and clamping the isolated portion with the cylindrical internal and external blades which moves relative to each other longitudinally of the wire before cutting. Therefore, there is no risk to damage the internal insulating material.
In addition, since the cutting point of the braided sheath may be freely changed by the position control of the cylindrical internal blades, the length of the braided sheath to be stripped off, which is determinedby the position of the cutting point, may be chosen quite freely.